The present invention relates to a process for the manufacture of an optical-fiber light sensor or panel, as well as to an optical-fiber light sensor or panel obtained by this process.
An optical-fiber panel is a luminous display or decoration or signalisation device which presents itself in the form of a plate, the generally plane front face of which constitutes the end of a relatively large or small number of optical fibers which traverse from front to rear the thickness of this plate so as to emerge, by their free end, flush with this front face which constitutes the surface intended to be seen.
At the rear and at a distance from this plate, these optical fibers are compacted into a bundle of optical fibers. This bundle receives light signals representing a display or other image, this image being reproduced on a large scale on the front face of the panel.
An optical-fiber light sensor is composed of a panel identical to that which has just been described, but utilizing either fibers made of synthetic material or mineral fibers in the case where this sensor is of parabolic shape, thus concentrating the solar light and heat energy. This sensor receives light information on its front face, this information representing, for example, the intensity of solar or ambient illumination, and transmits this light energy remotely to a processing component or directly to an optical-fiber panel via its bundle of optical fibers. The difference as compared with the aforementioned optical-fiber panel is thus essentially only a difference of function. In the text which follows, everything which will be stated in relation to an optical-fiber panel will apply like-wise to an optical-fiber sensor.
In an optical-fiber panel, each optical fiber thus traverses the thickness of the panel until it opens on the front face, which is visible, of the latter. The construction of these panels is currently undertaken by introducing, by manual or robotic means, one of the free ends of each optical fiber into a recess provided to this end in a perforated plane plate, which is capable of constituting the front plate of the light sensor or panel. The disadvantages of such a process are those of being either long and tedious, involving a manual construction, or too complex and costly, involving a robotic construction, so that it is finally poorly adapted to a profitable industrial exploitation, this being all the more so as it consists in a manufacture of optical fibers which are independent of that of the optical sensor or panel.
Moreover, this process does not permit the construction of panels of large size (for example 12 m.sup.2) which, in order to have a correct optical definition, must consist of a very large number of fibers (approximately 180,000). Now, the implantation fiber by fiber, manually or even by robotic means, would require a length of time incompatible with the essential industrial and economic requirements.
Moreover, in the optical-fiber panel obtained by such a process, which is described, for example, in the patent U.S. Pat. No. 3,853,658, the end of each optical fiber introduced into the front plate of the panel diffuses the light only over a small angular field. This is due to the fact that the optical fiber obtained by traditional linear manufacture is sheathed over its entire length including over its end. Consequently, the image formed on such a panel exhibits "black" spots or shadow zones impairing its quality. It is possible to remedy this only by an extremely tedious operation of machining each one of the ends of the fibers, in such a manner as to increase their angular field of diffusion up to angle values greater than or equal to 70.degree.. Nevertheless, the result obtained remains unsatisfactory.